Correct execution of thermal separation house/garage

Hello everyone,

we are currently working on the final details of the construction planning for our small house, and there are a few problem areas where I am not quite sure what the right approach is.

Primarily, I am concerned with the correct execution of the thermal separation between the house and the garage. The house is to be built on a (slight) slope, with the basement or lower floor almost embedded in the slope to the north, while to the south it will be completely open - all executed in WU concrete, with 24 cm walls (prefabricated walls + in-situ concrete) plus 14 cm XPS perimeter insulation. On top of this will stand a timber frame prefabricated house with 1.5 stories. In the basement/lower floor, a living area/granny flat and a utility room are to be created, all within the thermal envelope - the targeted standard for the entire house is KFW 55 (this is important to us).

Next to this insulated area, directly adjoining and connected via a (T30) door, there should be the (preferably uninsulated) garage. If relevant, the garage roof will be walkable & greened, as the side entrance (garden access) of the house is directly above it. For better orientation, I have attached a plan excerpt - however, this still shows the (not desired by me) execution of the garage as an insulated room.

The energy consultant has specified that there must be a separation between the house and garage, continuously through the roof, walls, and base slab. The separation is to be insulated with 140 mm XPS boards. As a result, a wall will be inserted on the garage side, thickness yet to be determined. The architect, however, is not enthusiastic about this idea and would rather advise a smaller joint with 2 cm insulation plus internal insulation.

From what I have read, the energy consultant’s approach would actually be the correct one, but I am not sure if it might bring its own problems.

For example, I do not know how the (condensation) water issue looks in such a semi-"core insulation"?

Are problems to be expected regarding the differential settlement of the components? My consideration was to insulate only the house’s base slab (140 mm XPS) and leave the garage’s base slab uninsulated.

How do you actually conceal such a building joint? Can you simply plaster over it, or is something else required?

Has anyone planned and implemented something (similar), and if so, what are your experiences?

Are there possibly other ways that lead to Rome?

Thank you!

Are there possibly other ways that lead to Rome as well?

But then probably without a stop in Bielefeld Congratulations on the two 850i

we are currently working on the final details of the construction planning for our small house, and there are a few problem areas where I am not quite sure what the right approach is. Primarily, I am concerned with the correct execution of the thermal separation between the house and the garage.

That may be the essential acute problem from your point of view, but you know the overall project – we do not. If you let us have a little more insight into the pot, probably much better advice can be given.

Uh, no, rather not, maybe you’ll find more problems in it, then we’ll have to replan everything.

No, seriously, attached are the further plans, full basement/cellar, ground floor as well as the side views, in case it might be helpful somehow.

And no, the big cars are just placeholders. Luckily, I’m a golf player, so there will also be room for a few bicycles in my future garage.

Ehm, no, better not, maybe you'll find more problems in it, then we'll have to reschedule everything.

You might be right about that - more at the earliest this evening ...

For the terrace doors around the dining table, I would reconsider which leaf of the part to be opened should be the sliding one. For the door at the bottom of the plan, I would choose the right one, which is closer to the kitchen, and for the door on the left of the plan, I would choose the upper one, which is closer to the sofa.

Thank you for the note - we also discussed it back and forth a bit. I would have done it as you suggested, but my wife thought that the other opening direction would be more comfortable to operate for right-handers like us, which makes sense to me. We are still "pondering" that.